This invention relates to a process for the preparation of optically active carbon compounds.
The process relates to the preparation of optically active carbon compounds from optically inactive hydrocarbons, with development of the chiral centers by the carbon-to-carbon linkages.
Chemical literature reveals only three examples of non-enzymatic, asymmetrical catalysis by way of C--C linkage. J. Furukawa et al. (Bulletin of the Chemical Soc. of Japan, Vol. 41, 155 (1968) describe the synthesis of optically active trimethyl cyclododecatrienes from pentadi-1,3-ene, using a catalyst of titanium tetra-menthozyl and diethyl aluminium monochloride at 40.degree.C. However, insufficient information is given regarding the yield of the optically active products and their optical purity and according to the indicated data, the yields are not higher than 10% and 4%, respectively. The authors themselves point out that the optical purities cannot be high, since the rotations are small.
H. Nozaki et al. (Tetrahedron Vol. 24, 3655 (1968) obtained trans-1-methyl-2-phenylcyclopropane from diazomethane and 1-methyl-2-phenyl-ethylene with a yield of optical product of less than 8% at 60.degree.C, with the aid of a catalyst consisting of an optically active cupric complex. Cuprous chloride catalysts with complex-bonded trialkyl or triaryl phosphite ligands were used by W. R. Moser (J. Amer. Soc. 91:15, 1135 (1969) for the synthesis of optically active cyclopropane derivatives from ethylene diazocetate and styrene. The ( (-)-tribornyl-phosphite)-cuprous chloride produced the corresponding cyclopropane derivatives with an optical yield of about 3% at 30 to 60.degree.C.
The optical purities of the compounds produced by the above methods are unsatisfactory, because, firstly, the inducing groups on the catalyst are exchanged during the reaction for inactive groups and, secondly, the reactions mentioned in the examples only proceed at relatively high temperatures.